Pampas – the Search Begins!
Black smut fungus found damaging C. jubata flowerheads in Ecuador. Image - Carlos Villamil
After surveys of pampas (Cortaderia selloana and C. jubata) in New Zealand found few natural enemies attacking the plant it was decided that potential biocontrol agents in the native range should be sought.In 2011 a multi-agency group, known as the National Pampas Biocontrol Initiative, was successful in gaining funds to allow this to happen.
The first task was to identify where in the native range of pampas in South America we should look for potential biocontrol agents. C. jubata was reported to be native to Argentina, Bolivia, Ecuador and Peru, with C. selloana native to Brazil, Argentina, Uruguay and Chile. However, it quickly became apparent that the taxonomy of Cortaderia is complex with many issues needing to be resolved. It is not possible to distinguish different species of Cortaderia by taxonomic features alone so molecular studies were essential. There was a suggestion in the literature that Argentina was the likely source of New Zealand pampas, so with the assistance of botanist Dr Carlos Villamil (Universidad Nacional del Sur, Argentina) we got samples from there first.
Molecular analysis revealed that none of the samples of C. jubata from Argentina matched C. jubata plants from New Zealand. “In fact the plants currently referred to as C. jubata are significantly different genetically, and have previously been in another species,” said plant population geneticist Gary Houliston. An American study had previously shown that invasive C. jubata from invaded regions in California, Hawai’i and New Zealand consisted of the same single clone that matched the most common clone identified in herbarium specimens from southern Ecuador. We confirmed that all New Zealand C. jubata matched this genotype and then searched for collaborators in southern Ecuador who could help with surveys to look for potential biocontrol agents. Luckily plant pathologists Dr Maria Eugenia Ordonez and Dr Charles Barnes, and entomologist Dr Alvaro Barragan (Pontificia Universidad Católica del Ecuador) were able to help. With Dr Villamil along to help identify the correct species, a preliminary survey of C. jubata was undertaken in April 2012. While the plants appeared to be generally quite healthy, a smut and a fly that damage the flowerheads were observed that are worth further study.
Trying to locate a match for C. selloana has been more challenging. None of the samples collected from Argentina, nor the single sample sourced from Chile, have proven to be a good match for New Zealand material with one exception. Some small infestations of C. selloana growing in Nelson and Southland are genetically different from C. selloana in the rest of New Zealand and are similar to Argentinean material. This material should be considered a third type of pampas for New Zealand. We have recommended these infestations should be eradicated, as they have the potential to make the pampas problem here even worse if they allow new genetic combinations to form, and/or if any biocontrol agents released down the track are unable to attack them. “Our plan is to now source samples from other parts of the reported native range to look for a match,” explained Gary.
We have also considered the feasibility of an inundative approach to pampas biocontrol using plant pathogens already present in New Zealand. “Unfortunately none of the pathogens found on Cortaderia have all of the characteristics necessary to make them a good candidate for development as a bioherbicide,” concluded Stan Bellgard. We are now looking at whether any of the endophytes/secondary pathogens already present on or in pampas leaves in New Zealand have the potential to disrupt any biocontrol agents that we may wish to introduce. We found a fungus (Epicoccum purpurascens) on pampas here which has been used overseas as a biocontrol agent to control peach rot (Monilinia spp.), hence the need to look into this further.
This project is funded by the National Pampas Biocontrol Initiative through a grant from the MAF Sustainable Farming Fund (11/049) supported by a number of co-funders including the National Biocontrol Collective.